Project 7: Role of Mineral Genesis, Dissolution, and Sorption on Arsenic Fate

与矿物基质有关的砷很少构成直接的环境风险，而在水相中活动的砷则对人类和环境健康构成潜在威胁。因此，控制固体对砷的封存也可以控制其相关风险。砷在固-水界面上发生的化学反应（包括吸附和解吸、沉淀和溶解、还原和氧化）不仅控制砷向水中的释放，而且构成除砷技术的基础。因此，本项目期望实现的对关键固-水界面处砷行为的基本理解的增强可以应用于砷污染的预防和修复。铁基固体通常用于从受污染的水中去除砷，并且是在天然好氧环境中与砷相关的典型固体。然而，我们目前的工作表明，它们是不稳定的，当放置在厌氧环境中，典型的许多含砷废物处置场。与硫化物有关的砷则相反，例如在受地雷影响的地点，从厌氧环境到有氧环境的转变刺激了砷的释放。因此，含铁和硫化物的矿物在不断变化的氧化还原环境中的行为是拟议工作的主要焦点。该项目的具体目标是确定1）砷与铁固体的关系和2）砷与硫固体的关系的机制和途径，并开发3）利用生物和地球化学矿物保留过程的工程干预方法，以最大限度地减少固体废物中的砷释放。这些感兴趣的固体-砷-水反应通常是微生物介导的，并且可以采取多个途径并导致多个最终固相， 不同的砷保留能力。由于相关过程的复杂性，该项目包括水地球化学、微生物学、化学动态建模、工艺工程和光谱学方面的专家。

Arsenic associated with mineral matrices seldom poses a direct environmental risk, whereas arsenic that is mobilized in the aqueous phase poses a potential threat to human and environmental health. Consequently, controlling arsenic's sequestration by solids also controls its associated risk. Chemical reactions of arsenic occurring at the solid-water interface (including adsorption and desorption, precipitation and dissolution, and reduction and oxidation) not only govern the release of arsenic into water, but form the basis of arsenic removal technologies. Thus, the enhanced fundamental understanding of arsenic behavior at critical solid-water interfaces that this project expects to achieve can be applied to both prevention and remediation of arsenic contamination. Iron-based solids are typically used to remove arsenic from contaminated water and are the typical solids with which arsenic is associated in natural aerobic environments. However, our current work has shown they are unstable when placed in the anaerobic environments that typify many arsenic-bearing waste disposal sites. The reverse is true for arsenic associated with sulfides, such as at mine impacted sites, where the shift from anaerobic to aerobic environments stimulates arsenic release. Thus, the behavior of minerals containing iron and sulfide when subjected to changing redox environments is the primary focus of the proposed work. The project's specific aims are to determine the mechanisms and pathways for 1) arsenic association with iron solids and 2) arsenic association with sulfur solids, and to develop 3) engineered intervention approaches that utilize biological and biogeochemical mineral retention processes to minimize arsenic release from solid wastes. These solid-arsenic-water reactions of interest are typically microbially mediated and may take multiple pathways and lead to multiple final solid phases with varying capacity for arsenic retention. Because of the complexity of the relevant processes, the project includes experts in aqueous geochemistry, microbiology, chemical dynamic modeling, process engineering and spectroscopy.